Friday, March 1, 2013

Tuned in

By Mark Hamer

We often list our large brains,
opposable thumbs, and developed vocal chords as defining biological traits that
make us human. Socially, our combined ability to communicate through speech,
develop complex relationships and recognize ourselves as individuals, distance
us from all other organisms on earth. But here are more subtle aspects of our
existence that go unexplored. Traits of our species that, though heard by most daily, go unnoticed or at
least under-appreciated. I’m talking about music. Music is a mysterious thing.
Its effects on human behavior can manifest itself as anything from a deep calm
to flailing around like a tempestuous banshee. Clearly there is something that
exists within these intentionally manipulated vibrations that is altering what
goes on in our heads. So let’s take a moment to appreciate music, and its
effects on the brain.

An awesome visual of a connectome, which diagrams neuronal circuits in the brain

Brain physiology is a complex and
often convoluted discussion point. We are all aware that, at its core, the
functional units of the brain are neurons. The human brain is estimated to
contain 100 billion neurons (that’s 100,000,000,000). Neuronal networks within
the brain work like telephone lines. They send information back and forth at
astonishing rates. Of course, like telephone lines, a single neuron usually is
not long enough to reach from the origin of the signal to the destination.
Instead, neurons are said to “synapse” with other neurons. That is, once a
point is reached where one neuron stops, another neuron picks it up. Telephone
poles don’t float in the air without support. They require telephone poles at
regular intervals. The telephone poles of the brain consist of a variety of
supportive cells known as glial cells. A single neuron is capable of receiving
signals from hundreds, even thousands of other neurons and transmitting it through to many more. Signals are received by dendrites and
sent through axons. When a signal is being transmitted through a neuron we call
it an action potential. Action potentials occur as the result of sufficient
stimulation of the neuron by the dendrites that have formed connections (i.e. synapsed)
to it. The action potential is then propagated along the axon by exploiting the
electrochemical voltage gradient that exists between the interior and exterior
of the cell. Think of this as the way electrons are passed from atom to atom in
our telephone wire example. Once this signal reaches the end of an axon it
stimulates the release of chemicals, known as neurotransmitters. Common
neurotransmitters include chemicals such as serotonin, dopamine and
acetylcholine. These neurotransmitters have diverse roles in brain physiology
but effectively they can be thought of as the intermediate chemical messenger
that transfers the signal between neurons.

The basic structure of a neuron

But we we’re talking about music
right? What does all this brain stuff have to do with music? Researchers have
taken a particular interest recently in the effects that music has on neurons
in certain regions of the brain. Direct links can be drawn between changes in
brain activity and nearly every aspect of human biology. So, if music is
affecting our brains it is very likely that it is affecting our bodies too. The
range of topics that could be covered in this blog is overwhelming. Instead of
sitting here listing all of the possible effects that music has on brain
physiology, I will instead focus on a couple of interesting discoveries that
have recently been made.

One of the articles that got me
interested in this subject was actually found while searching about the effect
of music on bodily physiology, specifically on blood pressure. As I read however
it became increasingly clear that what I was really reading was an article that
had much broader implications. On the surface, this article titled “Music
improves dopaminergic neurotransmission: demonstration based on the effect of
music on blood pressure regulation” attempts to explain a pathway through which
music is capable of decreasing blood pressure. It got me thinking though: if
music is causing a decrease in blood pressure, could it be that stress hormones
are the agent responsible? If this is the case, does music increase the capacity
of neurogenesis? After a quick search I found another article that answers just
this question.

We’ve all heard of something termed
the “Mozart effect”. The Mozart effect is the idea that, if exposed to
classical music during fetal development, the baby will have a step up on those
babies whose mom’s didn’t hold headphones against their bellies. However, it
might be better that mom just listen to the music herself. A second study found
that a decrease in stress hormones coincides with listening to classical music.
As us 502’ers know, decreasing stress has potentially long lasting effects on
neurogenesis, the ability for new neurons to form within the brain. So, when
mom’s relaxed the baby is too, and this promotes neurogenesis. These two
paper’s when read together thus show an extremely important relationship
between stress and music.

The
relationship between music and stress is a fairly straightforward concept. I’m
sure we all have that favorite band or album that, after a stressful day of
writing blog or papers on osmoregulation, instantly lets us chill out and
relax. But there’s a question that, in my mind, remained unanswered until I
really began to search. That is, why does music exist in the first place? We as
people interested in physiology should always ask ourselves what the functional
role of a behavior is.

The effect of music on systolic blood pressure

Currently, scientists are beginning
to cite music as being evolutionarily advantageous to humans. But how are these
broad claims being supported and what are their implications? Researchers at
Stanford may have been the first to support this idea with empirical evidence.
In their experiment they scanned the brains of people listening to the English,
late-baroque period composer William Boyce. One of the characteristics fundamental
to classical music is “the movement, which is defined as the primary
self-contained section of a large composition’’. Transitions between movements
provide a relevant way of modeling what is known as event segmentation. Event segmentation, as the name suggests, is
the partitioning of particular sensory events in to pieces that the brain is
capable of then storing or ignoring. Studying movement transitions allowed the
authors to discover differences in the activity of certain regions of the brain.
In this study activity was observed “in the ventral fronto-temporal network
associated with detecting salient events, followed in time by a dorsal fronto-parietal
network associated with maintaining attention and updating working memory.” This
discovery has fascinating implications. Most importantly is helps to describe a
model through which the brain processes salient stimuli. But what I found equally
intriguing was the fact that when you are listening to music, especially new
music, you are honing your ability to pick up on and pay attention to stimuli. What’s
even more amazing is that music is beginning to be discovered to have adult neurogenic
properties as well. Chew on that for a moment!

A 20 second video showing some of the interesting changes that

occur in the brain during a motion transition

At the beginning of this blog I
listed some physical and social attributes that are often used to describe
human beings. I believe that the beauty of music is that it utilizes all of
these and focuses them down in to a coherent manifestation of the human
condition. So go listen to some music, it really is good for you.